A touch screen device is an input device for entering data into a data processing system. The data provided to the system are indicative of a location on the panel. The user selects the location by contacting the panel. The device's operation may be based on the detection of forces and moments of forces applied to the panel by means of strain gauges. Such a device is known from, for instance, U.S. Pat. No. 4,558,757.
In the conventional device, the panel is mechanically coupled to a rigid frame by a suspension means (see column 3, line 63). Touching the panel gives rise to strain in the suspension means as a result of the reaction forces constraining the panel relative to the frame. The actual location whereto the force is applied, or of the magnitude of the force may be calculated from the strain's location and magnitude. To this end the strains are transformed into electrical signals by the strain gauges to be processed by the data processing means.
The frame itself has to be rigid in order to form an adequate reference system relative to which the forces are measured. The rigidity is of particular importance in order to enhance linear response of the gauges and in order to avoid hysteresis effects. The linearity of the gauges' response implies that only relatively simple calculations need to be performed by the data processing means and may therefore contribute to simplicity of the processing means or to high-speed performance.